Japanese Patent No. 5079655 (Patent Document 1) and Japanese Patent Application Laid-Open (JP-A) No. 2012-51005 (Patent Document 2), for example, disclose methods for manufacturing press-molded articles with a U-shaped cross-section profile (gutter profile).
In these press-molded article manufacturing methods, a metal sheet blank is held by a punch-side pad (also referred to hereafter as an inner pad) projecting from a punch and by a die-side pad (also referred to hereafter as a die pad) projecting from a die bottom of a die. The die is pushed in toward the punch side in this state, so as to mold the press-molded article. The occurrence of spring-back is thereby suppressed in the press-molded article.
In these press-molded article manufacturing methods, the punch-side pad projects from the punch when pushing the die in toward the punch side to mold side walls. Accordingly, slack portions (linear excess portions) arise in the metal sheet blank between shoulders of the punch-side pad and shoulders of the punch. These slack portions (linear excess portions) are slightly curved toward a front face side of the metal sheet blank.
The die-side pad and the die are then pushed further in toward the punch side to mold a top plate of the press-molded article. When this is performed, portions of the metal sheet blank that have been bent by the shoulders of the punch are pushed out toward a base end side of the side walls and become the side walls. A first moment toward the inside of the press-molded article therefore arises at a base end portion of each side wall of the press-molded article after demolding (see the arrow in FIG. 5(b) in Patent Document 2).
The slack portions (linear excess portions) are ultimately squashed between the punch and the die. However, prior to being squashed, each slack portion (linear excess portion) deforms by slightly curving so as to protrude toward the front face side of the metal sheet blank. A second moment toward the inside of the press-molded article therefore arises at both width direction end portions of the top plate of the press-molded article after demolding (see the arrow in FIG. 5(b) in Patent Document 2).
A third moment toward the outside of the press-molded article arises at ridge line portions of the press-molded article after demolding (see the arrow in FIG. 5(b) in Patent Document 2). However, the third moment is canceled out by the first and second moments, enabling spring-back of the press-molded article to be suppressed.